SACRAMENTO — If Jerry Brown runs for an unprecedented fourth term as governor of the Golden State, he would trounce all three likely Republican challengers in June’s open primary, according to a new Field Poll.

More than half of registered voters (52 percent) would pick Brown if the primary were held today, and nearly 6 in 10 registered voters say they approve of the job Brown is doing — the governor’s highest approval rating since taking office in January 2011 and an increase of 7 percentage points since July.

Only 11 percent of Californians would vote for former Lt. Gov. Abel Maldonado, and support for state Assemblyman Tim Donnelly and former George W. Bush administration official Neel Kashkari would be in the single digits, the poll finds.

Of the four candidates, only Donnelly and Maldonado have formally announced their intention to run. But both Brown and Kashkari, a former assistant treasury secretary from Orange County, are expected to announce in the coming weeks.

The top two finishers in next June’s primary, regardless of political party, will face off in November’s general election — the first time Californians have elected a governor this way.

“It’s going to be a very uphill fight for any candidate to defeat Jerry Brown next year,” said Dan Schnur, director of the Jesse M. Unruh Institute at the University of Southern California.

“The combination of the state’s voter registration and the lack of awareness that Californians have about the Republican candidates leads to a fairly predictable set of results,” he said.

Indeed, few voters surveyed by the Field Poll had formed an opinion on any of Brown’s Republican challengers.

Roughly 80 percent of voters are unfamiliar with Donnelly or Kashkari, who has never run for elected office before. More than 60 percent of voters have no opinion on Maldonado, who was appointed lieutenant governor by former Gov. Arnold Schwarzenegger but in 2010 lost his race for the seat to Gavin Newsom.

Dan Newman, a political strategist and adviser to Brown, said the poll’s findings align with the governor’s record and results.

“He not only silenced the critics, he won them over by doing what few thought possible: He restored fiscal stability, erased a deficit, reformed our school funding system, created jobs and led the way on climate change,” Newman said. “It’s entirely understandable that people prefer continued strong, effective leadership instead of abruptly turning California over to the tea party.”

The Field Poll surveyed 826 California registered voters from Nov. 14 through Tuesday. The poll has an overall margin of error of plus or minus 3.5 percentage points.

Oakland resident Nicholas Peraino said he plans to vote for Brown in June because the governor’s values are more in line with his own than the other potential candidates.

Peraino said his support for Brown solidified as the governor racked up victories in the Legislature and at the ballot box, including the passage of a tax initiative that stabilized state finances.

“Getting Prop. 30 passed was huge,” said Peraino, 30, who works for a labor union.

Among registered Republicans, Maldonado edged out Donnelly by a single percentage point, but Brown trails both men only slightly.

Ron Nehring, one of Maldonado’s advisers, said the candidate’s goals is not to beat Brown in June but to make it to the November general election and defeat him then. “We don’t have to come in first; we just need to make it to the runoff, and I’m confidant we’ll be in a strong position to do that,” Nehring said.

Donnelly, of Twin Peaks, is favored by voters who identify as strongly conservative. But surprisingly, even among voters who identify with the tea party, he garnered only 19 percent of the vote compared to Brown’s 26 percent, the poll found.

Jennifer Kearns, a spokeswoman for Donnelly, said she’s not surprised by the Field Poll’s results either. Historically, the poll tracks liberally, she said, noting that Donnelly led the Republican field in a separate poll released Wednesday by the Public Policy Institute of California.

That poll also showed Brown crushing his potential opponents, but by a smaller margin. The PPIC poll also found that Brown has a lower approval rating — 49 percent among likely voters — than the one recorded by the Field Poll.

Voter support for Kashkari is the lowest among the three potential Republican contenders. But Aaron McLear, one of Kashkari’s advisers, said the poll’s results are encouraging since he hasn’t formally announced yet.

“If Neel decides to run, he’ll have the resources he needs to communicate with voters,” McLear said. “I’d be more concerned if he were one of the other two contenders who have been openly running for a year now and with whom Neel is essentially tied.”

The race for second place in the June primary could come down to fundraising, political experts say.

Brown raised $2.8 million in the year’s first half and had more than $10 million cash on hand as of midyear.

Maldonado had raised just over $314,000 and had about $44,600 as of June 30, but he also had more than $47,900 in outstanding debts, effectively leaving him in the red.

Donnelly at midyear had raised about $83,100 and had about $27,418 cash on hand with about $13,000 in outstanding debts.

Since then, Brown has raised at least $5.6 million; Maldonado has raised at least $169,000; and Donnelly has raised at least $45,000.

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